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Active optics
Active optics is a relatively new technology for reflecting telescopes developed in the 1980s, which has more recently enabled the construction of a generation of telescopes with 8 metre primary ... > more -
Near-Earth object
Near-Earth objects (NEO) are asteroids, comets and large meteoroids whose orbit intersects Earth's orbit and which may therefore pose a collision danger. Due to their size and proximity, NEOs are ... > more -
Lunar space elevator
A lunar space elevator (also called a moonstalk) is a proposed cable running from the surface of the Moon into space. It is similar in concept to the better known Earth space elevator idea (a cable ... > more -
Presentism (philosophy of time)
In the philosophy of time, presentism is the belief that neither the future nor the past exists. The opposite of presentism is 'eternalism', which is a belief in things that are past and things that ... > more -
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible electromagnetic radiation. Above infrared in frequency comes visible light. This is the range in which the sun and stars similar to it emit ... > more -
Compton Gamma Ray Observatory
The Compton Gamma Ray Observatory (CGRO) was the second of the NASA "Great Observatories" to be launched to space, following the Hubble Space Telescope. The observatory was launched on the Space ... > more -
Outer space
Outer space, also simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace (and ... > more
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